I guess it was better the pressure blew out the mufflers and not back up through the heads. That must have been one heck of a BOOM. Did your BOV not open?
Everything was fine mechanically, big hp blower cars just don't like exhaust restrictions. We still completed that dyno pull. It just obliterated the mufflers around 5000rpms.
That is just not right! How big was the backfire? No normal kind of back pressure should be ever be able to blow out the turn downs. Were they aluminum and exhaust heat got to them?
That is just not right! How big was the backfire? No normal kind of back pressure should be ever be able to blow out the turn downs. Were they aluminum and exhaust heat got to them?
It wasn't a backfire. This was a smooth dyno pull on 28psi with the AFRs around 11.4 on C16. The pull was from around 4000-7400rpms. We heard a strange noise at the beginning of the pull, but with this much power, the pull is over very quickly. When we got out of the car, there was fiberglass packing material floating around in the air and some steel wool type substance landed about 30-feet behind the car and under some cardboard boxes which then caught on fire. We couldn't stop laughing! (despite the fact that the whole ordeal cost me quite a few bucks)
I asked around, and the general consensus among people that know a lot more about this stuff than I do is that a blower car making this much power (probably around 1300 at the crank) needs to get the exhaust out as quickly as possible. The bigger the better. Also, Aluminum is not the best material for collector mufflers. So our "safe" tune probably caused some of the exhaust to still be burning as it left the headers and the combination of heat & vibration gutted the mufflers. The guts of the mufflers then blew off the turndowns. Pretty crazy stuff!
Now it has 4" stainless mufflers on the collectors, and I haven't had any problems since. But boy is it LOUD!